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#
# Copyright (c) 2008-2009, REvolution Computing, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
.foreachGlobals <- new.env(parent=emptyenv())
# this is called to register a parallel backend
setDoPar <- function(fun, data=NULL, info=function(data, item) NULL) {
assign('fun', fun, pos=.foreachGlobals, inherits=FALSE)
assign('data', data, pos=.foreachGlobals, inherits=FALSE)
assign('info', info, pos=.foreachGlobals, inherits=FALSE)
}
# this explicitly registers a sequential parallel backend
registerDoSEQ <- function() {
setDoPar(doSEQ, NULL, info)
}
# passed to setDoPar via registerDoSEQ, and called by getDoParWorkers, etc
info <- function(data, item) {
switch(item,
workers=1L,
name='doSEQ',
version=packageDescription('foreach', fields='Version'),
NULL)
}
# this returns a logical value indicating if a parallel backend
# has been registered or not
getDoParRegistered <- function() {
exists('fun', where=.foreachGlobals, inherits=FALSE)
}
# this returns the number of workers used by the currently registered
# parallel backend
getDoParWorkers <- function() {
wc <- if (exists('info', where=.foreachGlobals, inherits=FALSE))
.foreachGlobals$info(.foreachGlobals$data, 'workers')
else
NULL
# interpret a NULL as a single worker, but the backend
# can return NA without interference
if (is.null(wc)) 1L else wc
}
# this returns the name of the currently registered parallel backend
getDoParName <- function() {
if (exists('info', where=.foreachGlobals, inherits=FALSE))
.foreachGlobals$info(.foreachGlobals$data, 'name')
else
NULL
}
# this returns the version of the currently registered parallel backend
getDoParVersion <- function() {
if (exists('info', where=.foreachGlobals, inherits=FALSE))
.foreachGlobals$info(.foreachGlobals$data, 'version')
else
NULL
}
# used internally to get the currently registered parallel backend
getDoPar <- function() {
if (exists('fun', where=.foreachGlobals, inherits=FALSE)) {
list(fun=.foreachGlobals$fun, data=.foreachGlobals$data)
} else {
if (!exists('warningIssued', where=.foreachGlobals, inherits=FALSE)) {
warning('executing %dopar% sequentially: no parallel backend registered',
call.=FALSE)
assign('warningIssued', TRUE, pos=.foreachGlobals, inherits=FALSE)
}
list(fun=doSEQ, data=NULL)
}
}
'%do%' <- function(obj, ex) {
doSEQ(obj, substitute(ex), parent.frame())
}
'%dopar%' <- function(obj, ex) {
e <- getDoPar()
e$fun(obj, substitute(ex), parent.frame(), e$data)
}
doSEQ <- function(obj, expr, envir, data) {
# note that the "data" argument isn't used
if (!inherits(obj, 'foreach'))
stop('obj must be a foreach object')
it <- iter(obj)
accumulator <- makeAccum(it)
for (p in obj$packages)
library(p, character.only=TRUE)
i <- 1
tryCatch({
repeat {
# get the next set of arguments
args <- nextElem(it)
if (obj$verbose) {
cat(sprintf('evaluation # %d:\n', i))
print(args)
}
# assign arguments to local environment
for (a in names(args))
assign(a, args[[a]], pos=envir, inherits=FALSE)
# evaluate the expression
r <- tryCatch(eval(expr, envir=envir), error=function(e) e)
if (obj$verbose) {
cat('result of evaluating expression:\n')
print(r)
}
# process the results
tryCatch(accumulator(list(r), i), error=function(e) {
cat('error calling combine function:\n')
print(e)
NULL
})
i <- i + 1
}
},
error=function(e) {
if (!identical(conditionMessage(e), 'StopIteration'))
stop(simpleError(conditionMessage(e), expr))
})
errorValue <- getErrorValue(it)
errorIndex <- getErrorIndex(it)
if (identical(obj$errorHandling, 'stop') && !is.null(errorValue)) {
msg <- sprintf('task %d failed - "%s"', errorIndex,
conditionMessage(errorValue))
stop(simpleError(msg, call=expr))
} else {
getResult(it)
}
}
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